Electromagnetic device



Oct. 17, 1944. R, D NELSON 2,360,511

ELECTROMAGNETIC DEVIS E Original Filed Nov. 13, 1941 A /Pozm/v D. A/Hso/vf 29491 BY Patented Oct. 17, 1944 UNITED STATES PATENT OFFICE ELECTROMAGNETIC DEVICE Original application November 13, 1941, Serial No.,

Divided and this application February 15, 1943, Serial No. 475,907

7 Claims.

This invention relates to electromagnetic devices such as transformers, chokes, and other devices of this general nature, and is a division of my application iiled November 13, 1941, Serial No. 418,876, for Electromagnetic devices.

Transformers have heretofore been made in which wound magnetic cores are employed. However, transformers having Wound magnetic cores frequently require a considerable amount of assembly work and often require very great care in order to avoid the danger of imparting mechanical stresses to the magnetic core after the magnetic core has been annealed, as these mechanical stresses adversely affect the magnetic characteristics of the cores thereby resulting in a lowering of the efiiciency of the transformer or other electromagnetic device.

This invention is designed to overcome the above noted defects and objects of this invention are to provide a novel form of electromagnetic device which has its core structure formed of wound magnetic ribbon, which is wound into closed cores which are thereafter cut into sections all of which are used in the completed device, in which no unusual care is required in the assembly of the parts of the device, in which no bending, machining, or other Working of the core structure is required after annealing, and in which short-circuiting of the laminations is avoided.

The invention in its broadest aspect permits the use of stacked magnetic laminations, or wound cores formed of magnetic ribbon which are subsequently cut into parts after winding, the resulting magnetic core structure being laminated throughout its entire extent.

Further objects are to provide an electromagnetic device in which there are relatively few joints in the core structure, in which the joints in the core structure are so formed that a substantially edge to edge contact of the adjacent laminations is obtained, thereby materially reducing the reluctance of the magnetic path, and in which these results are obtained in a very simple manner and with a very small amount of `lgood space factor is obtained for the conductingV winding.

Further objects are to provide a novel form of transformer or other electromagnetic device which is extremely simple to manufacture, and

in which the number of operations required in its production is materially reduced.

An embodiment of the invention is shown 1n the accompanying drawing, in which:

Figure l is a view, partly in section and partly broken away, showing a transformer.

Figure 2 is a sectional view on the line 2-2 of Figure 1.

In making the transformer, the central core is formed by winding a closed core of magnetic ribbon. This wound magnetic ribbon is then cut in half and the two sections are arranged bacl to back to form the central core portion l provided with outwardly extending end portions 2 projecting outwardly in opposite directions at each end of the central core.

The outer cores are formed of wound magnetic ribbon and are cut in half and the two halves are separated. The half sections forming the outer cores are indicated at 3 and each is provided with inwardly projecting end portions 4 which are spaced apart, as shown most clearly in Figure 2. These end portions 4 abut the side faces of the end portions 2 of the central core section and an edge to edge contact is obtained. It is preferable to grind the adjacent faces of the portions 2 and 4 to secure smooth, even faces and an accurate edge to edge contact. After the grinding has been completed, all of the cores are annealed and any burrs or wire edges that may result from the grinding or cutting are burned off, but if by any chance any remaining burrs or wire edges should be left after annealing, these may be readily removed by means of a wire brush or, in fact, they may be removed by a wire brush prior to annealing.

. It is not necessary to grind down the central portion of the central core l for it will be seen that the outer cores do not cross over the curved portions at the outer ends of the central core. Instead the outer cores terminate in the portions 4, see Figure 2, which do not cross over the curved l outer ends of the central core, see Figure 1.

The wound magnetic ribbons forming the outer vided between all of the faces of the clamping members and the laminated core structure.

The material used in the making of the cores is any suitable magnetic ribbon. It is preferable to use silicon steel which may be either hot rolled or cold rolled as this material has been found highly efcient in the manufacture of these transformers or other electromagnetic devices of this general nature, such as chokes for instance.

It will be seen that the lateral edges of the laminations of the central core have an edge to edge contact with the adjacent edges of the outer cores.

It is to be noted that the magnetic ilux travels lengthwise of the magnetic ribbon in substantially all portions of the core structure and this is the path having minimum magnetic reluctance due to the manner in which the particles of the magnetic ribbon are orientated during their manufacture. However, there is a small portion'of the magnetic path where the ux travels crosswise of the magnetic ribbon where it passes from the end portions of the central core into the outer i cores. This path of cross travel of the flux is very short and is confined to a very limited portion of the entire core structure.

It will be seen, therefore, that transformers and other electromagnetic devices have been disclosed by this invention which have a very small magnetic reluctance for the flux travel and which are extremely simple to make and which utilize the advantages of wound magnetic cores formed from magnetic ribbon, though allowing the conducting Vwinding to be wound in the ordinary simple manner without requiring any special processes for the winding of the conducting winding.

Ilt is to be noted that the substantially edge to edge contact between the laminations of the central and outer cores materially reduces the reluctance of the magnetic path.

It will be seen further that transformers or other electromagnetic devices constructed in accordance with this invention may be made with a very small number of operations and in a verysimple manner.

It is to be understood that wherever the expressions laminations or magnetic laminations are employed, it is intended that these expressions shall not be limited to stacked laminations but shall include any laminated structure whether it is formed by winding magnetic ribbon or by stacking magnetic laminations.

Although this invention has been described in considerable detail, it is to be understood that such description is intended as illustrative lrather than limiting, as the invention may be variously embodied and is to be interpreted as claimed.

I claim:

l. A core construction for an electromagnetic device comprising a core formed of magnetic laminations having oppositely extending, outwardly turned end portions at opposite ends thereof with the outer ends of the end portions spaced apart at each end of said core, and a second core structure formed in two parts of magnetic laminations having inwardly turned end portions whose latera1 edges are in close juxtaposition to the lateral edges of the outwardly turned portions of the first mentioned core, the inner ends of the inwardly turned end portions being spaced apart.

2. A core construction for an electromagnetic device comprising a core formed of magnetic laminations having oppositely extending, outwardly turned rend portions at opposite ends thereof withA the outer ends of the end portions spaced apart at each end of said core, and a secondv core structure formed in two parts of magnetic laminations having separate inwardly turned end portions whose lateral edges are in close juxtaposition to the lateral edges of the outwardly turned porti-ons of the first mentioned core. v

3. A core construction for, an electromagnetic device comprising a central core having two sections of magnetic laminations with the ends turned outwardly in opposite directions at opposite ends of the central core, and an outer core structure comprising magnetic laminations formed in two spaced apart sections on each side of the central core having eachsection on each sidek of the central core provided with inwardly turned ends, the inwardly turned ends of each section on opposite sides of the central'core having -their side faces in close juxtaposition to the side faces of the corresponding outwardly turned portions of the central core.

4. A core construction for an electromagnetic device comprising a central core having two sections of magnetic laminations with the ends turned outwardly in opposite directions at opposite ends of the central core, andan outer core structure comprising magnetic laminations formed in two spaced apart'sections on each side of the central core having each section on each side of the central core provided with inwardly turned ends, the inwardly turned ends of each section on opposite sides ofthe central core having their side faces in contact with the side faces of the corresponding outwardly turned portions of the central core with the laminations of the inwardly turned ends of the outer sections having substantially an edge to edge contact with the l laminations of the outwardly turned endsI of the central core.

`5. A core construction for an electromagnetic device comprising a central core having two sections of magnetic laminations with the ends turned outwardly in opposite directions at opposite ends of the y/central core, andan outer core ystructure comprising magnetic `laminations formed in two spaced apart sections on veach side of the central core having each section on each side of the ycentral core provided with inwardly turned endsythe inwardly turned ends being located at each end of each section of the outer core lstructure Vand beingspaced apart, the inwardlyturned ends of each section on opposite sides of the central core having their side faces in close juxtaposition to the 4side faces of the corresponding outwardly turned portions of the central core. y f' 6. A core construction for an electromagnetic device comprising a central core having two sections of magneticdamnations with the ends turned outwardly in opposite directions at opposite ends of the central core, and an outer core structure comprising magnetic laminations formed in two spaced apart sections on each side of the central core having each section on each side of the central core provided with inwardly turned ends, the inwardly turned ends being located ateach end of each section of the outer core structure and being spaced apart, the inwardly turned ends of each section on opposite side of the central core having their side faces in Contact with the side faces of the corresponding outwardly turned portions of the central core with the laminations of the'inwardly turned ends of the outer sections having substantially an edge to edge contact with the laminations of the outu wardly turned ends of the central core.

7. A core construction for an electromagnetic device comprising at least two core sections, each section consisting of Va plurality of 'layers of at magnetic ribbons with the iiat faces of the ribbons laid one upon the other, each section con- .fsisting of a main leg portion and end portions projecting at substantially right angles from the 

